How to do iteration in Python?

Iteration in Python is primarily achieved using for loops which allows you to execute a block of code repeatedly for each item in a sequence. A sequence object can be a list, tuple, string, or other iterable data structures.

Understanding Iteration with For Loops

The core concept behind iteration is to process each element within a collection, one at a time. Python’s for loop is exceptionally well-suited for this task. It systematically goes through each item in an iterable and executes the code block associated with it.

Basic for Loop Syntax

The syntax is straightforward:

for item in sequence:
    # Code to execute for each item

Here, sequence represents the iterable object, and item is a variable that gets assigned to each element of the sequence in turn during each iteration.

Iterating Through a List

As the provided reference states, you can use the for loop to iterate over the items contained within a list. Here's an example:

my_list = [10, 20, 30, 40, 50]

for number in my_list:
  print(number) # Output: 10, 20, 30, 40, 50 each in a new line

Key Aspects of for Loop Iteration

Feature	Description	Example Code
Iterable	Any object you can loop through.	my_list, "Hello", (1, 2, 3)
Item	Variable representing each element in sequence.	number in the list example
Block	Indented code to be executed on each item.	print(number) in the list example

Practical Examples and Insights

• String Iteration: You can iterate through characters in a string:

  my_string = "Python"
  for char in my_string:
      print(char) #Output: P, y, t, h, o, n each in a new line

• Tuple Iteration: Similar to lists, you can loop through elements in a tuple:

  my_tuple = (1, "apple", 3.14)
  for element in my_tuple:
      print(element) #Output: 1, apple, 3.14 each in a new line

• Using range() for Numeric Sequences: The range() function is often used with for loops to iterate a specific number of times:

  for i in range(5):
      print(i) # Output: 0, 1, 2, 3, 4 each in a new line

  range(5) creates a sequence of numbers from 0 to 4 (exclusive of 5), thus iterating 5 times.

• Nested Loops: For iterating over nested structures, you can nest for loops:

  matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
  for row in matrix:
      for num in row:
          print(num, end=" ")
      print() # Output: 1 2 3, 4 5 6, 7 8 9 each in a new line

  Additional Notes

• The for loop handles the iteration process automatically and efficiently.
• There are other mechanisms for iteration in Python, such as while loops and iterators/generators which might be needed in more advanced scenarios.
• Understanding the basic usage of the for loop, as described above, is essential for most common iteration tasks in Python.